This invention relates to an insulation insert assembly set between the main and auxiliary coils of a stator of, for example, an electric motor to effect insulation between the coils. This invention further relates to a method for manufacturing the insulation insert assembly.
A 2-phase motor, for example, is provided with a stator core and main and auxiliary coils wound about the stator core. An insulation insert assembly is generally put between the main and auxiliary coils to insulate both coils from each other. This insulation insert assembly generally includes a pair of insulation sheets prepared from, for example, polyester films and monofilaments and a pair of narrow connection rods for connecting said paired sheets, which are prepared from, for example, monofilaments. The sheets are substantially rectangular and are arranged in parallel spaced apart to an extent corresponding to the thickness of the stator core.
The stator is constructed in the following manner. A main coil is fitted to a stator core with the respective turns of the main coil inserted into the corresponding slots of the stator core. Next, the insulation insert assembly is securely attached to the stator core with the connection rods of the insulation insert assembly fitted into the corresponding slots of the stator core. The paired insulation sheets are set on both sides of the stator core. The fitting of the insulation insert assembly is effected by an automatic insertion device. Later the turns of the auxiliary coil are inserted into the corresponding slots of the stator core, thereby causing the paired sheets of the insulation insert assembly to be set between the main and auxiliary coils. When the auxiliary coil is inserted into the stator core slots, the central portion of the sheet located on the upper side of the stator core is pushed upward by the auxiliary coil. In this case, a gap is produced between this sheet and the stator core, thereby failing to assure complete insulation between the main and auxiliary coils.
To resolve the above-mentioned problem, the conventional insulation insert assembly is designed to suppress the lifting of the central portion of the respective sheets by reducing an interval defined between the paired connection rods. When, however, the connection rods are spaced from each other at a small distance, it is impossible to accurately locate both end parts of the respective sheets, because those relatively broader portions of the respective sheets which lie outside of the connection rods tend to be more freely bent. The above-mentioned drawback leads to a decline in the insulation efficiency of the insulation insert assembly. The Japanese patent disclosure No. 50-27006 sets forth an insulation insert assembly provided with three connection rods. This proposed insulation insert assembly suppresses the lifting of the paired sheets when the auxiliary coil is fitted into the slots of the stator core, and assures the accurate location of both end portions of the respective sheets. However, this proposed insulation insert assembly is still accompanied with the drawbacks that since three connection rods are provided, the proposed insulation insert assembly involves a large number of parts, raising the manufacturing cost and presenting difficulties in inserting the three connection rods into the corresponding slots of the stator core.